494 Miscellaneous. {Serr. 
[Instead of the usual 10 minutes pumping, required an hour to free the ship from water owing to 
eranckness, and having been 20 days on one tack. She has been pumped out generally 4 or 5 times, 
or about 170 strokes per diem. ] 
15 [38 53S.| 12 27E 51° 56° | guage. S. W. | {current 
18 [39 22 23 10 68 70 11.5 N. W. in the warm Cape 
[Since leaving the trades, the water pumped from the hold has been 2° to 5° warmer than the sea. | 
30 | 39 33 63 00 61 60 13.2 w.n.w! moderate. 
Augt. 6 | 28 35 83 O01 62 65 14.3 S. ditto. 
17 5 18 85 45 86 86 24.0 calm. |incabin 83° run 78°.5 
19 | 4 36 85 28 89 86 24.0 do. 83 
21 2 34 85 14 89 86 25.0 do. 84 _ +82 
23 0 59 84 57 8&9 86 25.0 do. 83 84 
29} 11 23N.} 85 34 88 84 26.5 S. W. |fresh. 
Sept. I | 20 14 87 08 86 86 S. W. |ditto, 
3 | Diamond | Harbour. 88 88 S. W. jlight. 
Average temperature of S. Tropic Indian Ocean, Air 81°.33 Sea, 81°.39 
N. Tropic to Diamond Hr. 86.4 85.35 
Average temperature of the whole voyage, Air 73.89 Sea, 74.17 
Do of former voyages— 
6 June to 18 Sept. 1827 71.71 
16 June to 6 Oct. 1828 71.28 
15 June to 18 Oct. 1829 70.16 
2 Aug. to 18 Dec. 1830 = 71.52 
22 Aug. to 16 Jan. 1831-2 74.57 
2.—On the Action of various Lights upon the Retina. By Sir D. Brewster. 
When the eyes are exposed to strong lights, objects cannot be seen of their true 
colours, and even lights of ordinary intensity produce a decided deterioration in 
the tints of a fine picture. Hence it is that we see paintings to most advantage when 
we view them through two blackened tubes held close to the eye, By this means 
the colours are not only more brilliant, but faint lights are brought out which 
would otherwise have been overpowered by the action of lateral light upon the 
retina. If we turna picture upside down, and look at it with the head inverted, 
a similar effect is produced, because the image is received upon a part of the retina 
which is not so frequently used ; and it is for the same reason that the colours of 
the sky and of the landscape near the horizon are so beautifully seen by looking at 
them either between the legs, or beneath the arm with the head inverted. 
It is well known that the human complexion is seen to greater advantage in 
candle, than in day-light, unless the complexions are very ruddy. This arises from 
there being so much more red in candle, than in day-light. There are certain states 
indeed, of the atmosphere, when dark-blue clouds prevail, in which the ordinary 
complexion appears to great disadvantage ; and persons in variable health are often 
described as looking ill, when the change arises from the prevailing colour of the 
clouds. 
When gas-lights were first introduced, it was acommon complaint among those 
who frequented the theatre that they injured the personal appearance of the audi- 
ence. This bad quality made them so unpopular, that a red colour was commu- 
nicated to the light by inclosing it in a reddish coloured glass. The effect, however, 
arose from the great quantity of light which was used, and from its influence upon 
the retina; and if the same intensity of light had been obtained either from oil or 
from candles, the same effect would have been produced. Our eyes are now so 
much accustomed to the use of strong lights that the retina is not so easily rendered 
insensible to the red rays, and the blue colour of the light is no longer complained 
of. It is, however, still observed, by those who have been for the first time exposed 
